The XMM Cluster Outskirts Project (X-COP): Thermodynamic properties of the intracluster medium out to R₂₀₀ in Abell 2319

¹ Dipartimento di Fisica e Astronomia, Università di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy
e-mail: vittorio.ghirardini2@unibo.it
² INAF, Osservatorio Astronomico di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
³ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
⁴ Max-Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
⁵ Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland
⁶ INAF – IASF-Milano, Via E. Bassini 15, 20133 Milano, Italy
⁷ CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
⁸ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
⁹ Centro de Estudios de Fisica del Cosmos de Aragon, Plaza San Juan 1, Planta-2, 44001 Teruel, Spain
¹⁰ Institut d’Astrophysique Spatiale, CNRS (UMR8617) Université Paris-Sud 11, Batiment 121, 91405 Orsay, France
¹¹ Harvard Smithsonian Centre for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
¹² Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy

Received: 9 August 2017
Accepted: 17 January 2018

Abstract

Aims. We present the joint analysis of the X-ray and Sunyaev–Zel’dovich (SZ) signals in Abell 2319, the galaxy cluster with the highest signal-to-noise ratio in SZ Planck maps and that has been surveyed within our XMM-Newton Cluster Outskirts Project (X-COP), a very large program which aims to grasp the physical condition in 12 local (z < 0.1) and massive (M₂₀₀ > 3 × 10¹⁴ M_⊙) galaxy clusters out to R₂₀₀ and beyond.

Methods. We recover the profiles of the thermodynamic properties by the geometrical deprojection of the X-ray surface brightness, of the SZ Comptonization parameter, and accurate and robust spectroscopic measurements of the gas temperature out to 3.2 Mpc (1.6 R₂₀₀), 4 Mpc (2 R₂₀₀), and 1.6 Mpc (0.8 R₂₀₀), respectively. We resolve the clumpiness of the gas density to be below 20% over the entire observed volume. We also demonstrate that most of this clumpiness originates from the ongoing merger and can be associated with large-scale inhomogeneities (the “residual” clumpiness). We estimate the total mass through the hydrostatic equilibrium equation. This analysis is done both in azimuthally averaged radial bins and in eight independent angular sectors, enabling us to study in detail the azimuthal variance of the recovered properties.

Results. Given the exquisite quality of the X-ray and SZ datasets, their radial extension, and their complementarity, we constrain at R₂₀₀ the total hydrostatic mass, modelled with a Navarro–Frenk–White profile at very high precision (M₂₀₀ = 10.7 ± 0.5^stat. ± 0.9^syst. × 10¹⁴ M_⊙). We identify the ongoing merger and how it is affecting differently the gas properties in the resolved azimuthal sectors. We have several indications that the merger has injected a high level of non-thermal pressure in this system: the clumping free density profile is above the average profile obtained by stacking Rosat/PSPC observations; the gas mass fraction recovered using our hydrostatic mass profile exceeds the expected cosmic gas fraction beyond R₅₀₀; the pressure profile is flatter than the fit obtained by the Planck Collaboration; the entropy profile is flatter than the mean profile predicted from non-radiative simulations; the analysis in azimuthal sectors has revealed that these deviations occur in a preferred region of the cluster. All these tensions are resolved by requiring a relative support of about 40% from non-thermal to the total pressure at R₂₀₀.